Stihl 020 T Manuel utilisateur

STIHL 020 T 1

Service Manual

020 T Chain Saws

This manual contains detailed

descriptions of all repair and

servicing procedures for 020 T

chain saws.

You should make use of the

illustrated parts list while carrying

out repair work. It shows the

installed positions of the individual

components and assemblies.

Microfilmed parts lists are always

more up to date than printed lists.

A fault on the machine may have

several causes. Consult the

"Troubleshooting Charts" when

tracing faults.

Refer to the "Technical Information"

bulletins for engineering changes

which have been introduced since

publication of this service manual.

Technical information bulletins also

supplement the parts list until a re-

vised edition is issued.

The special servicing tools mentioned

in the descriptions are listed in the last

chapter of this manual. Use the part

numbers to identify the tools in the

"STIHL Special Tools" manual.

The manual lists all special servicing

tools currently available from STIHL.

Service manuals and all technical

information bulletins describing

engineering changes are intended

exclusively for the use of STIHL

servicing dealers. They must not be

passed to third parties.

Always use original STIHL

replacement parts.

They can be identified by

the STIHL part number, the

STIHl

logo

and the STIHL parts symbol (

The symbol may appear alone on

small parts.

STIH

Servicing and repairs are made

considerably easier if the machine

is mounted on the assembly stand

(1). This enables the machine to be

swivelled to the best position for the

ongoing repair and leaves both hands

free.

The machine is secured to the stand

by means of the guide bar mounting

nut (after removing the sprocket

cover).

STIHL 020 T 2

CONTENTS

1. Specifications 3

1.1 Engine 3

1.2 Fuel System 3

1.3 Ignition System 4

1.4 Cutting Attachment 4

1.5 Special Accessories 4

1.5.1 For User 4

1.5.2 For Service 4

1.6 Tightening Torques 5

2. Troubleshooting

Charts 6

2.1 Clutch, Chain Drive,

Chain Brake and

Chain Tensioner 6

2.2 Engine 7

2.3 Ignition System 8

2.4 Rewind Starter 9

2.5 Chain Lubrication 9

2.6 Fuel System 10

3. Clutch, Chain Drive,

Chain Brake and

Chain Tensioner 12

3.1 Disassembling Clutch 12

3.2 Assembling Clutch 12

3.3 Chain Sprocket 13

3.4 Disassembling

Chain Brake 13

3.5 Assembling

Chain Brake 14

3.6 Chain Tensioner 15

4. Engine 16

4.1 Exhaust Muffler 16

4.2 Leakage Test 16

4.2.1 Preparations 17

4.2.2 Pressure Test 17

4.2.3 Vacuum Test 18

4.3 Oil Seals 19

4.4 Cylinder and Piston 20

4.4.1 Removal 20

4.4.2 Installation 21

4.5 Piston Rings 23

4.6 Crankcase 23

4.6.1 Removing the

Crankshaft 23

4.6.2 Installing the

Crankshaft 26

5. Ignition System 29

5.1 Spark Plug 29

5.2 Spark Plug Terminal 31

5.3 Ignition Lead 31

5.4 Ignition Module 32

5.4.1 Ignition Timing 32

5.4.2 Removing and

Installing 33

5.5 Flywheel 33

5.6 Ground Wire/

Short Circuit Wire 34

6. Rewind Starter 35

6.1 Routine Maintenance 35

6.2 Rope Rotor 35

6.3 Replacing the

Starter Rope 36

6.4 Replacing the

Rewind Spring 36

6.5 Tensioning the

Rewind Spring 37

6.6 Pawl 38

6.7 Starter Rope

Guide Bush 38

7. AV Handle System 39

8. Master Control/

Handle System 40

8.1 Master Control Lever 40

8.2 Choke/Throttle

Rods 40

8.3 Interlock Lever/

Throttle Trigger 41

8.4 Switch Shaft 41

8.5 Contact Springs 41

8.6 Double Lever

(Choke/Throttle) 42

8.7 Front Handle 42

8.8 Handle Housing 43

9. Chain Lubrication 44

9.1 Suction Hose/

Pickup Body 44

9.2 Vent Valve 45

9.3 Oil Pump 46

9.3.1 Removing and

Installing 46

9.3.2 Servicing 46

10. Fuel System 47

10.1 Air Filter 47

10.2 Carburetor 47

10.2.1 Removing and

Installing 47

10.2.2 Leakage Testing 48

10.2.3 Servicing 48

10.3 Carburetor

Adjustment 53

10.4 Pickup Body/

Fuel Hose 54

10.5 Tank Vent 55

10.6 Tank Housing 55

11. Special Servicing

Tools and Aids 57

11.1 Special Servicing

Tools 57

11.2 Servicing Aids 58

STIHL 020 T 3

1.2 Fuel System Carburetor:

Standard setting

High speed adjusting screw H:

Low speed adjusting screw L:

Carburetor leakage test

at gauge pressure:

Fuel tank capacity:

Octane number:

Fuel mixture:

Mix ratio:

Air filter:

Diaphragm carburetor

Back off approx. 1 turn

0.4 bar (5.8 psi)

0.37 I (0.8 US pt)

mind. 90 RON (USA/CAN: pump

octane min. 87 unleaded)

Regular brand-name gasoline

and two-stroke engine oil

50:1 with Stihl two-stroke

engine oil

25:1 with other brand-name

two-stroke, air-cooled

engine oils

Dual-ply synthetic fabric

or flocked wire mesh element

and foam element

35.2 cm

(2.15 cu.in)

40 mm (1.57 in)

28 mm (1.10 in)

7.41:1

1.6 kW (2.2 bhp)

1.8 Nm (1.3 Ib.ft)

at 7,500 r.p.m.

14,000 r.p.m.

2,800 r.p.m.

Crankshaft supported in heavy-

duty roller bearings, needle

cages on small and big ends

9 mm (0.35 in)

49 mm (1.93 in)

Pawl system

min. 1/2 turn

3.0 mm (0.12 in) dia., 800 mm

(31.5 in) long

Centrifugal clutch without linings

66 mm (2.60 in)

3,900 r.p.m.

0.5 bar (7.25 psi)

STIHL single-cylinder two-stroke engine with special

impregnated cylinder bore

Displacement:

Bore:

Stroke:

Compression ratio:

Power output:

Max. torque:

Max. permissible engine

speed with bar and chain:

Mean idle speed:

Bearings:

Piston pin diameter:

Connecting rod length:

Rewind starter:

Reserve pull on rope rotor:

Starter rope:

Clutch:

Diameter:

Clutch engages at:

Crankcase leakage

test

at gauge pressure:

under vacuum:

1. SPECIFICATIONS

1.1 Engine

STIHL 020 T 4

1.3 Ignition System

1.4 Cutting Attachment

1.5 Special Accessories

1.5.1 For User

1.5.2 For Service Shop

Type:

Air gap:

Ignition timing:

Advance angle:

Spark plug (suppressed):

Electrode gap:

Spark plug thread:

Length of thread:

Heat range:

Guide bars:

Bar tail:

Bar lengths:

Oilomatic chain:

Chain sprockets:

Chain speed:

Chain lubrication:

Oil feed rate (adjustable):

Oil tank capacity:

STIHL repair kit

7-tooth 3/8" P spur sprocket

8-tooth 1/4" spur sprocket

Elastostart

Air filter (flocked)

Carburetor parts kit

Gasket kit

Spur gear/tensioning screw kit

Electronic magneto ignition

(breakerless) with integral

trigger unit

0.25 mm (0.010 in)

2.0 - 2.8 mm B.T.D.C.

at 8,000 r.p.m.

24.7 -32.5° B.T.D.C.

at 8,000 r.p.m.

Bosch WSR 6 F or NGK BPMR 7 A

0.5 mm (0.020 in)

M14x1.25

9.5 mm (0.37 in)

200

Rollomatic

3005

30, 35, 40 and 45 cm

(12, 14, 16 and 18 in)

3/8" (9.32 mm) Picco-Micro

Optional:

1/4" (6.35 mm) Rapid-Micro

6-tooth spur sprocket for 3/8" Picco

Optional:

7-tooth for 3/8" Picco

8-tooth for 1/4"

18.6 m/s (61 ft/sec) at 10,000 r.p.m.

(with 6-tooth 3/8" P sprocket)

Speed-controlled reciprocating

oil pump, no oil feed at

idle speed. Additional manual

oil flow adjustment

4.0 - 10.5 cm3/min

0.14 -0.36 fl.oz/min) at 10,000 r.p.m.

0.24 I (0.5 US pt)

1129 900 5000

1129 640 2050

1129 640 2051

1128 190 3400

1129 120 1606

1129 007 1060

1129 007 1050

1129 007 1000

STIHL 020 T 5

Torque

Nm Ibf.ft

1.7 1.25

3.2 2.4

1.6 1.2

4.0 3.0

7.0 5.2

11.5 8.5

3.2 2.4

3.5 2.6

6.0 4.4

7.0 5.2

4.0 3.0

3.2 2.4

2.4 1.8

3.0 2.2

5.5 4.0

5.3 3.9

6.5 4.8

7.0 5.2

11.5 8.5

3.3 2.5

25.0 18.5

32.5 24.0

25.0 18.5

4.0 3.0

5.5 4.0

1.7 1.25

5.5 4.0

1.3 0.95

1.6 Tightening Torques

Plastoform screws are used for polymer components and "DG" screws for lightmetal components. These screws form a

permanent thread when they are installed for the first time. They can be removed and installed as often as necessary

without detrimentally affecting the strength of the screwed assembly, providing the specified tightening torque is

observed. For this reason it is essential to use a torque wrench.

Fastener

Spline screw

Nut

Collar nut

Screw assembly

Spline screw

Screw

Thread size

IS-P 4x14

IS-DG 4x15

IS-M 5x12

IS-M 5x20

IS-DG 4x15

IS-M 4x12

IS-M 5x12

IS-P 6x19

IS-P 5x20

IS-M 4x16

IS-P 4x10

IS-M 4x12

IS-M 4x16

IS-M 4x20

IS-M 5x12

IS-M 5x16

M 5

M 8x1

M 8x1 L

M 14x1.25

IS-P 5

IS-M 4x16

IS-P 4x14

IS-P 6x21.5

IS-P 4x10

For component

Chain catcher

Insert, chain brake

Handle molding

Muffler

Spiked bumper/crankcase

Muffler to cylinder

Insert

Oil pump

Annular buffer/front handle

Ring on housing

Fan cover/tank housing

Fan cover/crankcase

Segment/fan cover

Cover/chain tensioner

Cover/oil pump

Crankcase

Tank housing

Ignition module

Bar mounting flange/crankcase

Cylinder

Carburetor

Flywheel

Clutch

Spark plug

Annular buffer/handle housing

Annular buffer, front

Annular buffer, rear

Front handle/handle housing

Control lever/switch shaft

Remarks

2) 3)

Use the following procedure when refitting a P or DG screw in an existing thread:

- Place the screw in the hole and rotate it counterclockwise until it drops down slightly.

- Tighten the screw clockwise to the specified torque.

This procedure ensures that the screw engages properly in the existing thread and does not form a new thread.

1) Torque may be reduced by approx. 1 Nm (0.7 Ibf.ft) when refitting a screw in an existing thread

2) Screw must be secured with adhesive 0786 111 1101 (Loctite 243).

3) A washer must be fitted under the screw head.

Note: Screws secured with adhesive are easier to release if the adhesive is heated first with a hot air blower (hair dryer).

Exercise caution on polymer components.

STIHL 020 T 6

2. TROUBLESHOOTING CHARTS

2.1 Clutch, Chain Drive, Chain Brake and Chain Tensioner

Condition

Saw chain turns at idle speed

Loud noises

Chain sprocket wears rapidly

Chain wears rapidly

Chain does not stop immediately

when brake is activated

Cause

Engine speed too high

Spring hooks broken

Clutch springs stretched or

fatigued

Needle cage damaged

Clutch shoe retainer broken

Clutch shoes and carrier

worn

Chain not properly tensioned

Poor chain lubrication

Worn chain sprocket

Brake spring broken

Brake band stretched or

broken

Remedy

Readjust at idle speed

adjusting screw

(counterclockwise)

Fit new springs

Replace all clutch springs

Fit new needle cage

Fit new retainer

Fit new clutch

Tension chain as specified

Check chain lubrication and

rectify problem

Fit new sprocket

Fit new brake spring

Fit new brake band

STIHL 020 T 7

2.2 Engine

Always check and, if necessary, repair the following parts before looking for faults on the engine:

- Air filter

- Fuel system

- Carburetor

- Ignition system

Condition

Engine does not start easily, stalls

at idle speed, but operates

normally at full throttle

Engine does not deliver full

power or runs erratically

Engine overheating

Cause

Oil seals in crankcase

damaged

Manifold leaking

Cylinder base gasket leaking

Crankcase damaged (cracks)

Secondary air seepage through

poorly mounted or faulty manifold

Piston rings leaking or

broken

Muffler carbonized

Insufficient cylinder cooling.

Air inlets in fan housing

blocked or cooling fins on

cylinder very dirty

Remedy

Replace oil seals

Seal or replace manifold

Replace gasket

Replace crankcase

Mount manifold correctly or

replace

Fit new piston rings

Clean muffler (inlet and

exhaust), replace spark

arresting screen (if fitted)

Thoroughly clean all cooling air

openings and cylinder fins

STIHL 020 T 8

2.3 Ignition System

Warning: Exercise extreme caution while carrying out maintenance and repair work on the ignition system.

The high voltages which occur can cause serious or fatal accidents!

Ignition system in order.

Look for fault in fuel system and

carburetor.

yes

Replace ignition module. Does engine

now run after positive spark test?

Fit new flywheel.

Is spark test positive?

Use ohmmeter to check ignition lead

for break. If break is detected, replace

ignition lead. Does spark test now

produce sparkover?

Does flywheel appear to

be in good condition?

Fit new spark plug.Is air gap correct?

Adjust air gap (0.25 mm/0.010 in).

Is spark test positive?

Insert screwdriver in place of spark plug in spark plug

terminal and hold about 4 mm (1/8") away from

ground. Sparkover?

Replace faulty ignition lead of short

circuit wire. Repair contact spring.

Faulty insulation on ignition

lead or short circuit wire?

Clean spark plug and reset electrode gap.

Does spark test produce powerful spark?

Press terminal firmly onto spark

plug and fit spring if necessary.

Spark plug terminal firmly seated on spark plug?

Remove spark plug.

Is it in good condition?

yes

no yes

yes no

yes

STIHL 020 T 9

2.4 Rewind Starter

Condition

Starter rope broken

Rewind spring broken

Starter rope can be pulled out

almost without resistance

(crankshaft does not turn)

Starter rope is difficult to pull

and rewinds very slowly

Cause

Rope pulled out too vigorously

as far as stop or over edge –

i.e. not vertically

Normal wear

Spring overtensioned –

no reserve when rope is

fully extended

Very dirty or corroded

Guide peg on pawl or pawl

itself is worn

Spring clip fatigued

Starter mechanism is very

dirty (dusty conditions)

Lubricating oil on rewind

spring becomes viscous

at very low outside tem-

peratures (spring windings

stick together)

Remedy

Fit new starter rope

Fit new rewind spring

Fit new pawl

Fit new spring clip

Thoroughly clean complete

starter mechanism

Apply a few drops of kerosine

(paraffin) to spring, then pull rope

carefully several times until normal

action is restored

Remedy

Fill up with oil

Clean oil inlet hole

Wash intake hose and pickup body

(strainer) in white spirit and blow out

with compressed air; replace if

necessary

Clean or replace valve

Fit new pump piston and/or

new worm

Cause

Oil tank empty

Oil inlet hole in guide bar is

blocked

Intake hose or pickup body

(strainer) clogged or intake

hose ruptured

Valve in oil tank blocked

Teeth on pump piston and/or

worm worn

Condition

Chain receives no oil

2.5 Chain Lubrication

Important: In the event of trouble with chain lubrication system, always investigate the other possible sources of faults

before disassembling the oil pump.

STIHL 020 T 10

Condition

Machine losing chain oil

Oil pump delivers too

little oil

2.6 Fuel System

Condition

Carburetor floods;

engine stalls

Poor acceleration

Cause

Bore in pump housing

worn

Control screw and/or control

edge on pump piston worn

Bore in pump housing

Cause

Inlet needle not sealing.

Foreign matter in valve seat or

cone damaged

Inlet control lever sticking on

spindle

Helical spring not located on

nipple of inlet control lever

Perforated disc on diaphragm is

deformed and presses constantly

against inlet control lever Inlet

control lever too high (relative to

design position)

Idle jet "too lean"

Main jet "too lean"

Inlet control lever too low

(relative to design position)

Inlet needle sticking to valve

seat

Connecting bore to atmosphere

blocked

Remedy

Fit new pump housing

Fit new control screw and/or

pump piston

Fit new pump housing

worn

Remedy

Remove and clean or replace

inlet needle, clean fuel tank,

pickup body and fuel line if

necessary

Free off inlet control lever

Remove inlet control lever

and refit correctly

Fit new metering diaphragm

Set inlet control lever flush with

bottom of metering chamber

Back off low speed adjusting

screw slightly (see Carburetor

Adjustment)

Back off high speed adjusting

screw slightly (see Carburetor

Adjustment)

Set inlet control lever flush with

bottom of metering chamber

Remove inlet needle, clean and

refit

Clean bore

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